Spectroscopic studies on adsorbed metal carbonyls. Part 2. Interaction of [Ru3(CO)12] with silica, titania, and alumina

Abstract

The reactions between [Ru₃(CO)₁₂] and SiO₂, TiO₂, and Al₂O₃ have been studied by electronic and i.r. spectroscopy using ¹³C isotopic substitution. The complex [Ru₃(µ-H)(CO)₁₀(µ-OSi)] was initially generated on silica, but this oxidised in air to [Ru^II(CO)₂]_n(n= 2 or 3) species. Vacuum pyrolysis however generated another [Ru^II(CO)₂]_n species where n≃ 1 and some metallic ruthenium. Subsequent heating under CO generated Ru^III and Ru^IV monocarbonyl sites. The initial silica-type supported cluster was not observed on titania and alumina. The initial impregnation reactions generate similar species to the room-temperature air oxidation products on silica. The subsequent chemistry on titania is complex but evidence was obtained for four monocarbonyls on differing ruthenium centres (suggested as Ru^O, Ru^II, Ru^III, and Ru^IV) and a bridging carbonyl site.